CN1407061A - Optical aligning material for liquid crystal alignment membrane - Google Patents

Abstract

The invention discloses a photo-alignment material for liquid alignment film comprising a repeating unit represented by the formula 1 and at least one repeating unit selected from the repeating units represented by the formula 8 or comprises the repeating unit represented by the formula 1, at least one repeating unit selected from the repeating units represented by the formula 2, and at least one repeating unit selected from the repeating units represented by the formula 8, wherein more than 20% of the repeating units contains at least one functional group selected from photosensitive functional groups represented by the formula 5, in which the formula 1, formula 2, and formula 5 and formula 8 are as defined in the claims.

Description

Optical Alignment Materials for Liquid Crystal Alignment Films

field of invention

The invention relates to a photo-alignment material (photo-alignment materials) for a liquid crystal alignment film (alignment film). More specifically, the present invention relates to a photo-alignment material for liquid crystal alignment film, wherein the pretilt angle (pretilt angle) of the material can be freely controlled while providing the same or better alignment than rubbing process (rubbing process) The display quality of the material.

Background technique

The alignment of liquid crystals in a liquid crystal display changes according to an electric field induced by an externally applied voltage. This change in liquid crystal alignment determines whether external light entering the liquid crystal device is blocked or transmitted. Therefore, due to this property of the liquid crystal, a liquid crystal device can be driven. As a display device, the quality of a liquid crystal display is determined by properties that vary according to the alignment state of the liquid crystal, including light transmittance, response time, viewing angle, and contrast. Therefore, it is very important to uniformly control the alignment of liquid crystals in a liquid crystal device.

Alignment film refers to a layer of polymer material formed between liquid crystals, and a transparent conductive film made of indium tin oxide, in order to produce uniform alignment, that is, the orientation of liquid crystal molecules. After formation, the polymer layer is usually subjected to a mechanical process such as rubbing and other processes to control the alignment of the liquid crystals.

At present, in the preparation of liquid crystal displays, the methods used to achieve this uniform alignment of liquid crystals or to align liquid crystals in a given direction include placing a layer of polymer such as polyimide on a transparent conductive glass substrate, and using a rotating The surface of the polymer is rubbed by a roller at high speed, and the above-mentioned rotating roller is wrapped with a rubbing cloth made of nylon or rayon. By this rubbing method, liquid crystal molecules are aligned at a specific pretilt angle on the surface of the alignment film.

Since this rubbing method is basically the only method for easily and stably aligning liquid crystals, most manufacturers of liquid crystal displays generally use the rubbing method in mass production. However, the rubbing method has a problem in that scratches are generated on the surface of the liquid crystal alignment film due to mechanical friction, and static electricity that causes damage to the thin film transistor is generated. In addition, microfibers released from the rubbing cloth can cause defects in liquid crystal devices. The production quality of the device is thus reduced. In order to overcome the problems in the above-mentioned rubbing method and thereby improve productivity, as a new alignment technique, liquid crystal alignment by light irradiation such as UV ray irradiation has been proposed.

Recently, liquid crystal displays have become more and more widespread, and the use of liquid crystal displays is expanding beyond personal use such as notebook computers to home applications such as wall-mounted TVs. According to this trend, liquid crystal displays are required to have a high-quality picture and a large viewing angle. At the same time, in order to meet the requirements of liquid crystal display quality, the light alignment method is currently the focus of research.

However, by M.Schadt et al. (Jpn.J.Appl.Phys., Vol.31, 1992, 2155), Dae S.Kang et al. (USP 5464669) and Yuriy Reznikov (Jpn.J.Appl.Phys., Vol. 34, 1992, L1000), although advanced in concept, have not been commercialized because of difficulties in developing new materials to support these methods. A major reason for the difficulty is that the raw materials for the alignment film do not have sufficient processability for use in conventional methods of producing liquid crystal displays. Also, a display device using an alignment film formed by optical alignment has inferior display quality compared to a display device formed using a polyimide alignment film by a rubbing method.

Currently, the display quality of LCD monitors is continuously improving, and LCD monitors are considered to be the monitors with the best picture quality. In order to promote the development of liquid crystal displays in various fields, efforts to improve color reproducibility are also required. Improving the functionality of the alignment film can contribute to color reproducibility. For this reason, properly controlling the pretilt angle of liquid crystals has become the focus of research. So far, the pretilt angle of liquid crystals has been raised from a level of 1 to 3° to a level of 3 to 5°. For more natural colors, it is desirable to increase the pretilt angle to 7° or higher. However, the commonly used alignment material for the rubbing method has a pretilt angle of 3° to 5°. When the pretilt angle is increased or decreased from the above value, the alignment characteristics are considerably weakened or errors may occur due to scratches on the surface. In particular, although the pretilt angle was increased, it was difficult to obtain a stable pretilt angle over the entire surface of the screen, and partial unevenness was observed. Furthermore, it is considered very difficult to increase the pretilt without compromising other display qualities. New materials satisfying the above conditions are therefore required.

Contents of the invention

A feature of the present invention is to provide a new alignment material for liquid crystal alignment films, wherein the pretilt angle of the alignment material can be freely controlled at 1 to 10°, while providing an alignment equal to or better than that of the rubbing method. The display quality of standard materials.

According to one aspect of the present invention, there is provided an optical alignment material for a liquid crystal alignment film, the material comprising a repeating unit represented by the following general formula 1 and at least one repeating unit selected from a structure represented by the following general formula 8 units, wherein at least 20% of the repeating units contain at least one photoreactive functional group selected from the structure represented by the following general formula 5:

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom or a C _1-14 linear or branched alkyl group; Y is an oxygen atom or a C _2-14 alkylene group; R is a compound having a structure represented by the following general formula 3 Functional group:

Wherein R ₁ is selected from the functional group represented by the following general formula 4; R ₂ is selected from the functional group represented by the following general formula 5 and 6; R ₃ is selected from the functional group represented by the following general formula 7; k is an integer of 0 to 3; 1 is an integer of 0 to 5; and if there are multiple R ₁ or R ₂ , each R ₁ or R ₂ may be the same or different: Where n is an integer from 0 to 10,

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom, a C _1-13 alkyl or alkoxy group, or -(OCH ₂ ) _p CH ₃ , wherein p is an integer of 0-12, and m is an integer of 0-18;

Wherein n is an integer of 1-12.

According to another aspect of the present invention, there is provided a light alignment material for liquid crystal alignment film, the material contains repeating units represented by the following general formula 1, at least one selected from the structure represented by the following general formula 2 A repeating unit, and at least one repeating unit selected from a structure represented by the following general formula 8, wherein at least 20% of the repeating units contain at least one photoreactive functional group selected from a structure represented by the following general formula 5:

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom or a C _1-14 linear or branched alkyl group; Y is an oxygen atom or a C _2-14 alkylene group; R is a compound having a structure represented by the following general formula 3 Functional group:

其中X为氢原子、氟原子、氯原子、C_1～13烷基或烷氧基，或者-(OCH₂)_pCH₃，其中p为0～12的整数，m为0～18的整数；其中n为1～12的整数。Wherein R ₁ is selected from the functional group represented by the following general formula 4; R ₂ is selected from the functional group represented by the following general formula 5 and 6; R ₃ is selected from the functional group represented by the following general formula 7; k is an integer of 0 to 3; 1 is an integer of 0 to 5; and if there are multiple R ₁ or R ₂ , each R ₁ or R ₂ may be the same or different: Where n is an integer from 0 to 10,

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom, a C _1-13 alkyl or alkoxy group, or -(OCH ₂ ) _p CH ₃ , wherein p is an integer of 0-12, and m is an integer of 0-18; Wherein n is an integer of 1-12.

Detailed ways

Photoalignment materials according to the present invention relate to a copolymer of the maleimide type containing at least one material having a lower surface energy incorporated into the base polymer chain structure, such as a An aliphatic monomer, especially a cycloaliphatic monomer or a fluorinated monomer, to freely control the pretilt angle. In particular, such cycloaliphatic or fluorinated monomers are characterized by the absence of photoreactive groups. These surface energy-lowering monomers can be substituted at the terminal positions of the side chains or at other positions. However, according to the present invention, the above-mentioned monomers are directly linked to the polymer main chain, because it is more effective to achieve proper and free control of the pretilt angle of the liquid crystal.

Therefore, the alignment material of the present invention is a copolymer based on a maleimide-type monomer containing a maleimide-based repeating unit represented by the following general formula 1, and at least one selected from The repeating unit of the structure represented by the following general formula 8, or the copolymer contains a maleimide-based repeating unit represented by the following general formula 1, at least one kind of repeating unit selected from the structure represented by the following general formula 8 unit, and at least one repeating unit selected from the structure represented by the following general formula 2:

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom or a C _1-14 linear or branched alkyl group; Y is an oxygen atom or a C _2-14 alkylene group; R is a compound having a structure represented by the following general formula 3 Functional group:

其中n为0～10的整数，

Wherein R ₁ is selected from the functional group represented by the following general formula 4; R ₂ is selected from the functional group represented by the following general formula 5 and 6; R ₃ is selected from the functional group represented by the following general formula 7; k is an integer of 0 to 3; 1 is an integer of 0 to 5; and if there are multiple R ₁ or R ₂ , each R ₁ or R ₂ may be the same or different:

Where n is an integer from 0 to 10,

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom, a C _1-13 alkyl or alkoxy group, or -(OCH ₂ ) _p CH ₃ , wherein p is an integer of 0-12, and m is an integer of 0-18;

Wherein n is an integer of 1-12.

The repeat unit of formula 8 contains no side chain R groups. They can form copolymers or terpolymers together with the maleimide-based monomers represented by the general formula 1, or can be combined with the maleimide-based monomers represented by the general formula 1 and at least one of the general formula The monomers represented by 2 together form a copolymer. By introducing such aliphatic or fluorinated monomers into the main chain structure, the electrical properties of the alignment material and the display performance of the liquid crystal display can be improved.

Preferably, the proportion of repeat units containing at least one photoreactive group is adjusted to preferably at least 20% of the polymer, more preferably at least 30% of the polymer.

In the printing method for forming the photo-alignment film, the polymer for the photo-alignment material of the present invention is dissolved in a solvent, and then coated on a TFT substrate or a color filter substrate instead of the conventional one for the rubbing method. Polyimide. The alignment of the liquid crystals is thus carried out by polarized ultraviolet exposure using a 3KW mercury lamp instead of the conventional rubbing method. In this method, the exposure energy is typically 200 to 2000 mJ/cm ² . Generally, when the exposure energy is greater than 50mJ/cm ² , the liquid crystal can be aligned. The irradiation of ultraviolet rays is performed by an oblique irradiation method, that is, ultraviolet rays are irradiated onto the surface of the alignment film inclined at a given inclination angle to induce a pretilt angle of the liquid crystal. This process is equivalent to controlling the intensity and amount of friction in the traditional friction method of adjusting the pretilt angle.

Description of the preferred embodiment

The present invention will now be described in further detail with reference to the following examples. The purpose of these examples, however, is to illustrate the invention and should not be construed as limiting the scope of the invention.

1) Synthesis of light alignment materials

Example 1

Photoalignment materials with the following repeating unit structures were synthesized:

10 g (0.10 mol) of maleic anhydride and 10.1 g (0.09 mol) of aminophenol were added to 100 ml of toluene and stirred at room temperature for 2 hours to prepare an amic acid-type intermediate. The resulting solution was added to 100 ml of acetic anhydride, and dehydrated with 0.41 g (0.005 mol) of sodium acetate (CH _COONa ) at 95 ° C for 4 hours to obtain 4-acetoxyphenyl maleimide with a yield of 50%.

Then, in an acetone solvent at 65°C, using 0.35g AIBN (2,2'-azobisisobutyronitrile) as a polymerization initiator, 10g (0.043mol) of the above-mentioned synthesized 4-acetoxyphenyl maleic acid The imide was radically polymerized with 4.2 g (0.025 mol) of acetoxystyrene and 1.8 g (0.017 mol) of vinylcyclohexane for 4 hours to form the terpolymer described below.

将1g(0.003mol)上述合成的聚合物和1.2g(0.01mol)三乙胺加入到20ml1-甲基-2-吡咯烷酮(pyrrolidinone)中。然后向其中加入1.4g(0.007mol)4-甲氧基肉桂酰氯并在室温下搅拌1小时，如下所述得到本实施例的对准材料，产率为70％。 Deprotection of the resulting terpolymer with 5 g of p-toluenesulfonic acid (p-TsOH) in a mixture of methanol and acetone in 1 liter of methanol and acetone at 80°C for 5 hours gave a polymer having the following backbone structure, yielding The rate is 85%.

1 g (0.003 mol) of the polymer synthesized above and 1.2 g (0.01 mol) of triethylamine were added to 20 ml of 1-methyl-2-pyrrolidinone (pyrrolidinone). Then 1.4 g (0.007 mol) of 4-methoxycinnamoyl chloride was added thereto and stirred at room temperature for 1 hour to obtain the alignment material of this example as follows, with a yield of 70%.

Example 2

Photoalignment materials with the following repeating unit structures were synthesized:

The polymer backbone was synthesized in the same manner as described in Example 1. That is, 10g (0.043mol) of 4-acetoxyphenylmaleimide synthesized by the same method as described in Example 1, 4.2g (0.025mol) of acetoxystyrene, 1.6g (0.017mol) ) 3,3,3-trifluoropropene and 0.35 g of AIBN as a polymerization initiator were added to acetone, and radically polymerized at 65° C. for 4 hours to form a terpolymer. The resulting terpolymer was deprotected in the same manner as described in Example 1 to obtain the final polymer backbone having the following structure with a yield of 85%.

Then, 1 g (0.003 mol) of the polymer main chain synthesized above was dissolved in 20 ml of 1-methyl-2-pyrrolidone. Add 1.2 g (0.001 mol) of triethylamine and 1.4 g (0.007 mol) of 4-methoxycinnamoyl chloride as side chains to the solution, and stir at room temperature for 1 hour to replace the side chains attached to the main chain . The final photoalignment material was obtained with a yield of 70%.

Example 3

Photoalignment materials with the following repeating unit structures were synthesized:

The polymer backbone was synthesized in the same manner as described in Example 1. That is, 10 g (0.043 mol) of 4-acetoxyphenylmaleimide synthesized in the same manner as described in Example 1, 3.2 g (0.018 mol) of trifluoroethyl acrylate and as a polymerization initiator 0.35 g of AIBN was added to acetone and free radically polymerized at 65°C for 4 hours to form a copolymer as described below.

The resulting copolymer was deprotected in the same manner as described in Example 1 to obtain a polymer main chain having the following structure with a yield of 70%.

Then, 2 g (0.006 mol) of the polymer main chain synthesized above was dissolved in 20 ml of 1-methyl-2-pyrrolidone. 2 g (0.02 mol) of triethylamine and 2.8 g (0.014 mol) of 4-methoxycinnamoyl chloride as side chains were added to the solution and stirred at room temperature for 1 hour to replace the side chains attached to the main chain. The final photoalignment material was obtained with a yield of 60%.

Example 4

Photoalignment materials with the following repeating unit structures were synthesized:

The polymer backbone was synthesized in the same manner as described in Example 1. That is, 10 g (0.043 mol) of 4-acetoxyphenyl maleimide synthesized by the same method as described in Example 1, 2.24 g (0.018 mol) of 4-vinylcyclohexene 1,2- Epoxide and 0.35 g of AIBN as a polymerization initiator were added to acetone, and polymerized at 65° C. for 4 hours to form a polymer. The obtained polymer was deprotected in the same manner as described in Example 1 to obtain the following polymer main chain with a yield of 50%.

The side chains were synthesized as described below. First, 1g (0.006mol) of 4-carboxybenzaldehyde was reacted with 0.79g (0.006mol) of thionyl chloride in dichloromethane for 40 minutes, then in 50ml of pyridine at room temperature, with 0.79g (0.006mol) of propane Ethyl acetate was reacted for 3 hours. Subsequent acylchlorination of the product afforded the intermediate ethyl trans-chlorocarbonylcinnamate in 50% yield. This intermediate was reacted with 0.98 g (0.006 mol) of 4-hydroxybenzoic acid in aqueous NaOH/DMSO (dimethylsulfoxide) solution at room temperature for 2 hours to obtain the following side chain structure in 60% yield.

4.1 g (0.01 mol) of the side chain synthesized above were acid chlorinated. The resulting product 1 g (0.005 mol) of the polymer synthesized above and 2.1 g (0.02 mol) of triethylamine were dissolved in 20 ml of 1-methyl-2-pyrrolidone and stirred at room temperature for 1 hour. The final alignment material was thus obtained with a yield of 60%.

Example 5

Photoalignment materials with the following repeating unit structures were synthesized:

The polymer backbone was synthesized in the same manner as described in Example 1. That is, 10g (0.043mol) of 4-acetoxyphenylmaleimide synthesized by the same method as described in Example 1, 4.2g (0.025mol) of acetoxystyrene, 2.04g (0.017mol) ) 5-vinyl-2-norbornene and 0.35 g of AIBN as a polymerization initiator were added to acetone, and polymerized at 65° C. for 4 hours to form a polymer. The resulting terpolymer was deprotected in the same manner as described in Example 1 to obtain the following polymer main chain with a yield of 85%.

Then 1.7 g (0.005 mol) of the side chain synthesized by the same method as described in Example 1 was acyl chlorinated. The obtained product 1 g (0.002 mol) of the polymer prepared above and 0.73 g (0.007 mol) of triethylamine were dissolved in 20 ml of 1-methyl-2-pyrrolidone and stirred at room temperature for 1 hour. The final alignment material was thus obtained with a yield of 60%.

Example 6

Photoalignment materials with the following repeating unit structures were synthesized:

10 g (0.10 mol) of maleic anhydride and 13.7 g (0.1 mol) of aminoethylphenol were added to 100 ml of toluene and stirred at room temperature for 1 hour to prepare an amic acid-type intermediate. The resulting solution was dehydrated with 4.1 g (0.05 mol) of sodium acetate at 85° C. to obtain 4-acetoxyphenylethylmaleimide with a yield of 80%.

With an equivalent ratio of 1:0.6:0.2:0.2, 10 g of the above-mentioned synthesized 4-acetoxyphenylethylmaleimide was mixed with 4-acetoxystyrene, n-butyl acrylate and trifluoroethyl acrylate (trifluorooxymethlaerylate) was mixed and added to acetone, and then 0.35 g of AIBN was added as a polymerization initiator. They were polymerized at 65°C. The acetoxy groups in the resulting tetrapolymer were deprotected with 0.01 equivalent of p-toluenesulfonic acid in a mixture of methanol and acetone at 80°C for 5 hours to obtain a polymer backbone with the following structure in a yield of 70%.

2 g (0.007 mol) of the polymer synthesized above and 2.5 g (0.025 mol) of triethylamine were dissolved in 20 ml of 1-methyl-2-pyrrolidone. Then 4.7 g (0.013 mol) of 4-hexylcinnamoyl chloride was added thereto and stirred at room temperature for 1 hour. The final alignment material is thus synthesized.

2) Preparation of liquid crystal display and performance evaluation of liquid crystal display

Each of the photoalignment materials prepared in the above examples was dissolved in a mixture of 1-methyl-2-pyrrolidone and 2-butoxyethanol. The resulting solutions of the respective photo-alignment materials were coated on the TFT substrate and the color filter substrate by a printing method to form a photo-alignment film. These films were then exposed to polarized ultraviolet light with a 3KW mercury lamp. Prepare 15 " liquid crystal display according to the method that is usually used for making liquid crystal display. Except above-mentioned exposure process that liquid crystal is oriented, carry out all steps with the method that liquid crystal display is usually used. Then evaluate prepared each 15 " liquid crystal The basic electro-optical properties of a display as a display, such as contrast, response time, viewing angle, and brightness. The results are listed in Table 4.

According to the same method as above, a unit box of 1" was prepared with each light alignment material of the above embodiment. The voltage holding ratio (voltage holding ratio) and residual DC of the prepared unit box were measured. The results are listed in Tables 1 and 2 middle.

Prepare a 1" unit cell (unit cell) with each optical alignment material in the above-mentioned embodiment. Prepare an antiparallel cell (antiparallel cell) with a cell gap of 55 μm in a manner in which the liquid crystal alignment direction of each substrate is opposite. According to ( a) The crystal rotation method was used to measure the pretilt angle of each antiparallel cell. The results are listed in Table 3.

In each case, a liquid crystal for TN mode TFT-LCD supplied by Merck (NJ, USA) was used.

Comparative example 1

Using polyimide (SE 7992, supplied by Nissan Chemicals, JP), which is widely used as an alignment material, a 15" liquid crystal display and a 1" cell were prepared in the same manner as above. Measure their electro-optic properties, voltage maintenance ratio, residual DC and pretilt angle, and list them in Tables 1-4.

Comparative example 2

Using a photo-alignment material having the following molecular structure as described in Korean Patent Application Laid-Open No. 2000-8633, a 15" liquid crystal display and a 1" cell were prepared in the same manner as above. Their electro-optical properties, voltage maintenance ratio and residual DC were measured, and listed in Tables 1-4.

Table 1

voltage maintenance ratio Measuring temperature Room temperature (25°C) 60℃ Example 1 97.9% 94.7% Example 2 99.1% 97.5% Example 3 99.5% 98.0% Example 4 99.0% 96.9% Example 5 99.1% 95.7% Example 6 99.3% 97.1% Comparative example 1 99.1% 95.2% Comparative example 2 97.5% 92.4%

^* Measured under the condition of 1V and 60Hz frequency, the voltage maintenance ratio is 64 microseconds.

Table 2

remaining DC Maximum ΔC Example 1 21.5×10 ^-9 F Example 2 11.2×10 ^-9 F Example 3 9.7×10 ^-9 F Example 4 15.7×10 ^-9 F Example 5 10.3×10 ^-9 F Example 6 9.5×10 ^-9 F Comparative example 1 31.2×10 ^-9 F Comparative example 2 55.2×10 ^-9 F

^* Residual DC is relatively evaluated by comparing at the point where the capacitance difference (ΔC) is the largest at the same voltage.

table 3

Pretilt exposure angle Exposure energy Pretilt Example 1 30° 500mJ/ ^cm2 0.7° 1000mJ/ ^cm2 1.1° Example 2 30° 500mJ/ ^cm2 1.3° 1000mJ/ ^cm2 2.5° Example 3 30° 500mJ/ ^cm2 4.5° 1000mJ/ ^cm2 6.2° Example 4 30° 500mJ/ ^cm2 3.2° 1000mJ/ ^cm2 4.8° Example 5 30° 500mJ/ ^cm2 3.4° 1000mJ/ ^cm2 5.1° Example 6 30° 500mJ/ ^cm2 5.1° 1000mJ/ ^cm2 8.5° Comparative example 1 friction depth Pretilt normal(-1)mm 4.6° normal 4.1° normal(+1)mm 3.5° Comparative example 2 exposure angle Exposure energy Pretilt 30° 500mJ/ ^cm2 0.3° 1000mJ/ ^cm2 0.6°

^* Test method

.Determination of pretilt angle by crystal rotation method

.Based on the best standard, adjust the friction depth by increasing or decreasing the height of the rotating roller. (+1) mm indicates the case of increased friction compared with the standard (respectively).

.The exposure angle is defined as the incident angle between the ray (light) and the normal vector of the substrate.

. The exposure energy is measured by measuring the irradiation intensity of the radiation light within the wavelength range of 240 to 350 nm while changing the radiation time.

Table 4

Electro-optic performance of 15″ TFTLCD contrast Response time (ms) Brightness (cd/m ² ) angle of view right left top/bottom Example 1 198 31 204 58/58 45/＞60 Example 2 205 26 196 59/58 45/＞60 Example 3 200 29 208 59/58 45/＞60 Example 4 211 32 201 58/58 45/＞60 Example 5 210 30 205 59/59 45/＞60 Example 6 215 29 212 58/59 45/＞60 Comparative example 1 200 35 200 58/58 45/＞60 Comparative example 2 185 32 205 58/59 45/＞60

^* Average values measured at 9 different locations on the screen are recorded as contrast and brightness.

As can be seen from Table 1 above, Examples 1 to 6 according to the present invention show improvement in voltage sustaining ratio, especially at 60°, compared with the alignment material for the rubbing method. The remaining DC results were also improved in the examples of the present invention compared to the rubbed alignment material. Residual DC is an important performance of display quality stability of the display. In particular, it is considered to be a major factor related to an image sticking phenomenon that prevents natural display of moving images. The voltage maintenance ratio, together with residual DC, is also considered to be an important factor related to the image sticking phenomenon, and furthermore, it is also considered to be a key factor related to display reliability.

From the pretilt angle test results described in Table 3, it can be seen that the pretilt angle of the liquid crystal can be freely controlled by selecting the type of photoreactive substituent and changing the conditions of the exposure method. The pretilt angle is an important factor in the presentation of natural colors and uniform image quality across the entire screen of a large-scale display, as well as the aforementioned electro-optical performance. The commonly used alignment material for the rubbing method has (a) a pretilt angle of 3° to 5°. When the pretilt angle is increased or decreased from the above value, alignment characteristics are considerably weakened or errors occur due to scratches on the surface. In particular, although the pretilt angle is increased, it is difficult to obtain a stable pretilt angle over the entire surface of the screen and partial unevenness is observed. Furthermore, it is considered very difficult to increase the pretilt without compromising other display qualities. Can confirm by the result of embodiment and comparative example, according to the present invention, by adjusting the photoreactive group in the molecular structure of light alignment material and simply changing the condition of exposure method, as exposure energy and angle, can be in 1～ The pre-tilt angle can be freely controlled within 10°. In addition, as shown in Table 4, the electro-optic performance of the optical alignment material according to the present invention is equivalent to or better than that of the alignment material for the rubbing method.

Therefore, as described above, according to the present invention, it is possible to provide an optical alignment material for a liquid crystal alignment film in which the pretilt angle of the material can be freely controlled while providing a display equivalent to or superior to an alignment material using a rubbing method. quality.

Although there have been illustrated and described in detail what are considered to be the preferred specific embodiments of the present invention, those skilled in the art should understand that the present invention is not limited to these specific embodiments without departing from the true scope of the present invention. , changes, improvements and substitutions can be made to its various elements.

Claims (4)

1. A light alignment material for a liquid crystal alignment film, the material contains a repeating unit represented by the following general formula 1 and at least one repeating unit selected from a structure represented by the following general formula 8, wherein at least 20% The repeating unit contains at least one photoreactive functional group selected from the structure represented by the following general formula 5:

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom or a C _1-14 linear or branched alkyl group; Y is an oxygen atom or a C _2-14 alkylene group; R is a compound having a structure represented by the following general formula 3 Functional group:

Wherein R ₁ is selected from the functional group represented by the following general formula 4; R ₂ is selected from the functional group represented by the following general formula 5 and 6; R ₃ is selected from the functional group represented by the following general formula 7; k is an integer of 0 to 3; 1 is an integer of 0 to 5; and if there are multiple R ₁ or R ₂ , each R ₁ or R ₂ may be the same or different:

Where n is an integer from 0 to 10,

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom, a C _1-13 alkyl or alkoxy group, or -(OCH ₂ ) _p CH ₃ , wherein p is an integer of 0-12, and m is an integer of 0-18;

Wherein n is an integer of 1-12. 2. A light alignment material for a liquid crystal alignment film, the material contains a repeating unit represented by the following general formula 1, at least one repeating unit selected from a structure represented by the following general formula 2, and at least one Repeating units selected from the structure represented by the following general formula 8, wherein at least 20% of the repeating units contain at least one photoreactive functional group selected from the structure represented by the following general formula 5:

Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom or a C _1-14 linear or branched alkyl group; Y is an oxygen atom or a C _2-14 alkylene group; R is a compound having a structure represented by the following general formula 3 Functional group: Wherein R ₁ is selected from the functional group represented by the following general formula 4; R ₂ is selected from the functional group represented by the following general formula 5 and 6; R ₃ is selected from the functional group represented by the following general formula 7; k is an integer of 0 to 3; 1 is an integer of 0 to 5; and if there are multiple R ₁ or R ₂ , each R ₁ or R ₂ may be the same or different:

Where n is an integer from 0 to 10, Wherein X is a hydrogen atom, a fluorine atom, a chlorine atom, a C _1-13 alkyl or alkoxy group, or -(OCH ₂ ) _p CH ₃ , wherein p is an integer of 0-12, and m is an integer of 0-18;

Wherein n is an integer of 1-12. 3. The optical alignment material of claim 2, wherein the alignment material contains a styrene-based repeating unit among the structures represented by the general formula 2. 4. The photo-alignment material according to claim 1 or 2, wherein the alignment material contains a cinnamate group in the structure represented by the general formula 5 as a photo-reactive group.